The Cash Discount percent can be found in Setup > Setup POS & POS Devices.
The Cash Discount Formula is the Non Cash Payment Numerical Value / (1+ Non Cash Payment Numerical Value). For example if the NCP is 3.75%, then Cash Discounting is .0375 / (1 + .0375) = .0361... or 3.61%.
The Cash Discount percent will only display to the nearest 10th (example 3.61%) however the calculation on the data side of the software will use the full calculation result (example 0.036144578313253).